CD4 vs. Viral Load: What's in a Number?

What’s in a Number? : CD4 vs. Viral Load

Viral Load and CD4 Count

If you’re beginning HIV testing or treatment, you’ll learn to keep a sharp eye on your viral load and CD4 count. These two counts speak volumes about your HIV and immune system health. They provide important information on virus progression, therapy response, and help determine whether to begin HIV treatment.

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The Human Immune Alarm Bell

CD4 cells, also called T-cells, are like the alarm bells of the immune system. They alert the immune system to invading viruses and bacteria. Certain receptors on the CD4 cell make them a prime target for HIV infection. Infection lowers CD4 count. Lower CD4 count means a weaker immune system.

A normal CD4 count ranges from 500-1,000 cells/mm3. According to, a count of fewer than 200 cells/mm3 is one of the qualifications for an AIDS diagnosis.

Measuring HIV

Viral load is the best gauge of the level of HIV in the body. It is measured as the number of copies of HIV-1 per milliliter of blood plasma (copies/mL). According to the U.S. Department of Health and Human Services (HRSA), the lowest levels of detectable viral load are about 40-75 copies/mL. The highest measure can be over 500,000 copies/mL.

Low viral load means lower amounts of HIV activity. The goal of HIV therapy is to lower the viral load to levels below 40-75 copies/mL. It’s important to know that just because viral load may fall below these levels, does not mean HIV is gone from the body.

When Therapy Begins

CD4 count, the measure of immune system health, is the major factor in deciding whether to begin HIV therapy. Treatment guidelines recommend that therapy should begin when CD4 counts fall below 350 cells/mm3.

Treatment may also be considered for patients with CD4 counts up to 500 cells/mm3 if they have a high viral load, or if they are experiencing a rapid drop in CD4 cell count.

Types of Therapy

HIV therapy is called antiretroviral therapy (ART) or highly active antiretroviral therapy (HAART). It consists of the combination of at least three antiretroviral drugs (ARV) to keep the virus from spreading.

Slowing the spread of HIV gives the immune system and CD4 count time to recover. Three drugs are used in order to reduce the likelihood of the virus developing resistance.

Numbers Can Fluctuate

Be careful of attaching emotions to single test results. Numbers can often vary. For example, after initial HIV infection, viral load peaks. The immune system then responds and lowers the number to a base level.

CD4 levels can also vary. The time of day, illness, infection, and recent vaccinations can all affect CD4 and viral load count. This is why trends in results matter much more than individual test results.

Early Treatment and Transmission

Recent studies cited by the World Health Organization (WHO) show the benefits of beginning therapy early. This is when CD4 counts are higher than 350 cells/mm3.

According to the studies, starting ART when above 350 cells/mm3 reduces the risk of AIDS and tuberculosis. It also reduces the risk of developing non-AIDS-defining illnesses, such as liver failure and heart disease. Another trial showed that earlier treatment can reduce the risk of sexual transmission of HIV to non-infected partners.

Don’t Forget Your Vitamins

Nutrition and food safety are vital to living well with HIV. And fortunately, some studies have shown that nutritional supplements can help increase CD4 counts for patients.

In a study published by the Journal of Acquired Immune Deficiency Syndromes, researchers found micronutrient/vitamin supplements could significantly improve CD4 cell count in HIV patients who are also taking HAART.

A separate study showed that probiotic yogurt may help increase CD4 count slightly in HIV/AIDS patients by limiting gastrointestinal infections.

Checking The Numbers

The HRSA notes that CD4 and viral load monitoring happen about every three to six months. The schedules of each may differ slightly. Viral load requires more frequent monitoring. Viral load and CD4 monitoring increases when treatment begins. When treatment becomes effective, monitoring becomes less frequent.

HIV treatment has come a long way in recent years. An effective ART and attention to healthy living will help to keep your CD4 count high and viral load count low.

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